That word of course is M-O-N-E-Y. Imagine you're a high tech exec and you want to move from that Marxist hellhole, California, to low-tax Freedom-Loving Texas. So here's the notice you're going to send out to your gay married employees:
Thank for your years of loyal service. Our company will be moving to a new state, and if you want to come with us, the state we're moving too will treat your present marriage as non-existent for all state law purposes.
Doesn't have a very good ring to it. Worse yet, you might be gay yourself, so you'd have to telecommute or something.
Now in the old days an executive could simply apply the rule of simply not caring about the employees, but these days, no, particularly in high tech. So you're probably going to tough it out in the California GuLAG for at least a few more yeas until the Land o' Freedom figures out that it's gonna be more attractive to business if it treats all of your married employees with equal dignity.
Add to that a bunch of lost conventions etc. in non-marriage equality states due to boycotts, and before long, people are going to change their minds, as their fear of Teh Gay is washed away by the love of Teh Lucre
Take my state, Oregon. We foolishly passed an anti-marriage equality constitutional amendment back the day of Teh Gay Menace. Now, our arch-rival, a state very much like us (except it is ruled by the Lidless Eye of He who Must not Be Named), known as Washington State in the common tongue, but as Mordor to the wise, allows marriage equality.
Now, with the 1,000 federal benefits of marriage available as of yesterday to your company's employees in Washington State (i.e. the Land where the Shadow Lies) and exactly ZERO, ZILCH, BUPKIS available in the Beaver State -- where are you gonna go with your factory? I'm thinking the Minas Morgul Chamber of Commerce is gonna get a new member!